TOsEnum and COsDescr do not contain information for Windows Server 2016 yet and report such a system as Windows 10.

The TOsVersionInfoExW.wProductType field is set to 3 (VER_NT_SERVER) and should provide the required indicator. (This was also used to patch TOSVersion with 10.2 Tokyo.)Additional information about the server type (e.g. Server Core) may be available via the registry: Software\Microsoft\Windows NT\CurrentVersion\InstallationType

It would be nice if you could update this field with the next version.